Telex is the brainchild of computer science researchers at the University of Michigan and the University of Waterloo in Canada, who presented their anti-censorship concept at the recent USENIX Security Symposium in San Francisco. "This has the potential to shift the arms race regarding censorship to be in favour of free and open communication," says J Alex Halderman, assistant professor of computer science and engineering at the University of Michigan and one of Telex's developers.
"The Internet has the ability to catalyse change by empowering people through information and communication services. Repressive governments have responded by aggressively filtering it. If we can find ways to keep those channels open, we can give more people the ability to take part in free speech and access to information."
Today's typical anti-censorship schemes get users around site blocks by routing them through an outside server called a proxy. But the censor can monitor the content of traffic on the whole network, and eventually finds and blocks the proxy, too. "It creates a kind of cat-and-mouse game," says Halderman, who was at the blackboard explaining this to his computer and network security class when it hit him that there might be a different approach – a bigger way to think about the problem.
Here's how Telex would work: users install Telex software, downloading it from an intermittently available Web site or borrowing a copy from a friend. ISPs outside the censoring nation deploy equipment called Telex stations. When a user wants to visit a blacklisted site, he or she would establish a secure connection to an HTTPS Web site, which could be any password-protected site that isn't blocked; this is a decoy connection. The Telex software marks the connection as a Telex request by inserting a secret-coded tag into the page headers. The tag utilises a cryptographic technique called "publickey steganography".
The user's request passes through routers at various ISPs, some of which would be Telex stations. These stations would hold a private key that lets them recognise tagged connections from Telex clients. The stations would divert the connections so that the user could get to any site on the Internet.
The researchers are at the proof-ofconcept stage. They've been using it for their daily Web browsing for the past four months and have tested it with a client in Beijing who was able to stream YouTube videos, even though the site is blocked in China.
Source: University of Michigan